Load a layout's variables and conditions even when they arrive after it

lib/src/data/data_manager.dart

@@ -1418,7 +1418,8 @@ class DataManager {
 
     // Process Layouts
     SDKPublishLayout? layout;
-    if (model!.layouts.containsKey(layoutID)) {
+    final bool isCached = model!.layouts.containsKey(layoutID);
+    if (isCached) {
       DebugLogger.instance.printInfo(
         '\tLayout [$layoutID] is already cached. Skipping download.',
         name: name,
@@ -1446,8 +1447,6 @@ class DataManager {
           name: name,
         );
       }
-
-      model.layouts[layoutID] = layout;
     }
 
     assert(layout != null, 'Layout should not be null at this point.');
@@ -1545,6 +1544,13 @@ class DataManager {
       );
     }
 
+    // Add a downloaded layout only once its variables and conditions are in
+    // the model. A CodelesslyWidget builds a layout as soon as the model has
+    // it, and only loads the layout's variables and conditions then, so a
+    // layout added first would render without them if anything rebuilt the
+    // widget while they were still downloading.
+    if (!isCached) model.layouts[layoutID] = layout!;
+
     await emitPublishModel();
     savePublishModel();
 

lib/src/ui/layout_builder.dart

@@ -156,16 +156,37 @@ class _CodelesslyLayoutBuilderState extends State<CodelesslyLayoutBuilder> {
     }
   }
 
+  /// The layout's variables and conditions that [loadLayout] last loaded.
+  SDKLayoutVariables? loadedVariables;
+  SDKLayoutConditions? loadedConditions;
+
   @override
   void didUpdateWidget(covariant CodelesslyLayoutBuilder oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (oldWidget.layout.id != widget.layout.id ||
         oldWidget.canvasId != widget.canvasId ||
-        oldWidget.layout.lastUpdated != widget.layout.lastUpdated) {
+        oldWidget.layout.lastUpdated != widget.layout.lastUpdated ||
+        didVariablesOrConditionsChange(context)) {
       loadLayout(context);
     }
   }
 
+  /// Whether the publish model has different variables or conditions for
+  /// this layout than [loadLayout] last loaded. They can arrive after the
+  /// layout, e.g. when the layout was cached without them, or be published
+  /// on their own.
+  bool didVariablesOrConditionsChange(BuildContext context) {
+    final SDKPublishModel? model = context
+        .read<Codelessly>()
+        .dataManager
+        .publishModel;
+    if (model == null) return false;
+    bool changed(Object? loaded, Object? current) =>
+        !identical(loaded, current) && loaded != current;
+    return changed(loadedVariables, model.variables[widget.layout.id]) ||
+        changed(loadedConditions, model.conditions[widget.layout.id]);
+  }
+
   /// Loads the layout into the [nodeRegistry] and updates the
   /// [CodelesslyContext] with the node values.
   void loadLayout(BuildContext context) {
@@ -219,6 +240,8 @@ class _CodelesslyLayoutBuilderState extends State<CodelesslyLayoutBuilder> {
       }
     }
     final publishModel = context.read<Codelessly>().dataManager.publishModel!;
+    loadedVariables = publishModel.variables[widget.layout.id];
+    loadedConditions = publishModel.conditions[widget.layout.id];
 
     final Map<String, VariableData> variablesMap =
         publishModel.variables[widget.layout.id]?.variables[widget.canvasId] ??